This invention relates to an apparatus for carefully and accurately controlling the thermal history of a glass gob between the molten glass hearth and the molds during glass manufacturing.
One prevailing cause of defects in a product during glass manufacture is improper or non-uniform temperature. Such temperature variations may usually be attributed to a lack of control over the environmental conditions of the glass during the manufacturing operation. If the finished product is cracked or chipped, the glass itself may be too cold. If the finish is oval-shaped, flattened or pinched, the glass could be too hot. In U.S. Pat. No. 3,416,908, issued Dec. 17, 1968, entitled "Environmental Control System for Glass Manufacturing" by George I. Goodwin and Robert C. Coblentz, a solution to some of the problems of environmental control was set forth. In this patent, a means to maintain control over temperature, pressure and humidity were disclosed, whereby the thermal history of glass could be predetermined for consistent quality and increased production. The invention described in that patent was directed to environmental control of the glass or machine parts by "modified air" during the glass manufacturing process. It set forth a significant step in obtaining better glass products at increased production rates without relying on prior, rather ineffective, methods of simply circulating outside air.
It has been discovered, however, that in order to obtain complete control over a glass manufacturing system, the temperature of the glass between the hearth containing the molten glass and the molds must also be considered and controlled. While U.S. Pat. No. 3,416,908 suggested that modified air, obtained by the method set forth in that patent, could be fed into the chute down which the glass gobs fell from the hearth to the molds to control the temperature of the gob as it passes through the chute, it does not have the degree or speed of control desired for optimum uniformity. Because of the speed with which the gob moves along the chute under the acceleration of gravity, it is desirable to use a more direct and faster means of controlling the temperature of the gob to supplement the use of the modifying air, as suggested in the above patent.
Means have been suggested from time to time for maintaining a constant and uniform thermal history of a glass gob between its point of shear and the mold. For example, Whittemore (U.S. Pat. No. 1,310,225) teaches the use of a heating cup to contain individual severed gobs of glass which are heated by electrical coils and surrounded by a pressurized air bath. Wadsworth (U.S. Pat. No. 1,323,507) also teaches a temporary cup which catches a severed gob. Electric heaters heat an entire secondary block supporting the cup. Unfortunately, neither of these apparatus provide an automatic system for controlling the temperature of the glass, and both involve time delays reducing the production of glass.